Chapters - Frame Indexing

(Optional step)

To speed-up the pre-authoring process, DVD-lab displays the MPEG GOP (Group of Pictures) timecode in the Chapter Points area and in the preview. However DVD-lab will always remember the exact chapter placement and then during compiling it can automatically create Frame Index and match the desired position of chapters to the correct frame number.

Chapters accuracy
The usual error for chapter placement is about +/- 0.25 second. This is the best DVD can offer since Chapter Points must be on an MPEG I-frame marker which comes every 15 frames or so. When you are adding chapters to movie manually (using the cursor and plus sign) DVD-lab will stick to closest I-frame.

The Frame-Indexing will make sure the chapters will be placed within this accuracy.

All you need to know
If you don't want to read any further, then all you need to know is this:

This option will make sure that the Chapters will be added with frame accuracy and therefore they are not dependent on the GOP timecode. If the Frame-Index has not yet been created for the Movie, it will be generated just before the compile process starts and all your chapters will be translated to frames.

You can stop just here or read further if you need more information.

More reading about Frame-Index

Movie with existing index
A movie which has been indexed will show a Green diamond in the small icon in Assets when loaded. A new movie will not yet have an index, so it will not show this Green diamond flag.

Adding chapters
It doesn't matter if you add chapters with index available or not. DVD-lab is built so that you can Frame-Index a movie anytime without re-creating chapters. So you can add chapters the same way as before and then let DVD-lab create an index afterwards, for example during DVD compilation. Once Chapter Points have frame information, they will show a green diamond instead of red chapter point as shown here.

While the GOP timecode is in format HH:MM:SS the Frame based timecode is HH:MM:SS:FF where the FF are frames. Also, the frame number of the Chapter Point will be shown above in red. For NTSC users the time is shown in Non-Drop Frame format.

Indexing the movie
Automatic - DVD-lab does this for you. That's easy. When you go to Compile, enable Frame-Index Chapters.

Manual - Right-click on the movie and select Chapters-Frame-Index All Chapters

Manually create Frame-Index	If the index file for this mpeg is not found it will be created

When a Frame Index is created all previous chapters will be switched to Frame mode (green diamond):

Note: If you change the movie file in any way (transcode, re-encode, cut etc...) you have to also delete or manually generate the Frame index again. Using a frame index that was created for different file will place all chapters to wrong location.

Compilation
If you like to use Frame-Index for Chapter Points you will have to enable "Create/Use Frame-Index ..." in the compile window. If you don't enable it, a GOP timecode will be used even if you have index created.

Time calculation
Normally the GOP timecode and the displayed Frame timecode should be close, but sometimes there may be a slight discrepancy of a few seconds or so if the MPEG is in drop-frame format - this is nothing to worry about. The Frame displayed timecode is calculated from the frame number, frame-rate and pulldown. In rare cases, the GOP timecode and the Frame-Index based timecode may differ by more than a few seconds. The Frame-Index based timecode is the accurate one.

Manually adjusting the frame number.
In most cases the Chapter Points using Frame Code will occur exactly where you want them. Sometimes, especially if you use automatic Chapter Points, some Chapter Points may be placed one I-frame early or later than desired. In GOP timecode you may adjust time lag by +/- 1second, but this doesn't work for Frame Code. You can either delete the Chapter Point and try to create a new one 1 I-frame back (or forward as needed) or you can also directly adjust the frame index in the Set Chapter Lag dialog. An I-frame is usually 15 or 18 frames apart.